Spark-plug



R. L. HULL.

SPARK PLUG,

APPLlCATlON FILED NOV. 28, 1919.

1,388,343. Patented Aug. 23, 1921 IN VEN TOR EM L, HULL.

A TTORNEY UNITED STATES BAY L. HULL, OF SAN FRANCISCO, CALIFORNIA.

SPARK-PLUG.

Specification'of Letters Patent.

Patented Aug. 23, 1921.

Application filed November 28, 1919.' Serial No. 341,188.

To all whom it may concern:

Be it known that I, RAY L. HULL, a citizen of the United States, and a-resident of the city and county of San Francisco, State of California, have made a new and useful inventionto wit, Improvements in Spark- Plugs; and I do hereby declare the following to be a full, clear, concise, and exact description of the same.

This invention relates particularly to a modified form of spark plug for internal combustion engines.

The principle object of this inventionis to reduce the exposed area of porcelain within the cylinder and expose it to the immediate action of the spark upon which carbon and the waste products of combustion can be deposited.

It is a further object that the porcelain may be removed from the retaining shell without removing the shell from its position in the cylinder wall.

Another object contemplates a construction and arrangement of parts whereby the porcelain and insulating block may be spaced away from the retaining shell to allow for expansion and contraction, as well as to provide a more perfect insulatlon.

A still further object resides in providing a plug which is simple and inexpensive to manufacture, efficient and durable in use.

In this specification and the annexed drawings, the invention is disclosed in the form considered to be the best, but it is to be understood that the invention is not limited to such form, because it may be embodied in other forms, and it is also to be understood that in and by the claim following the description it is desired to cover the invention in'whatever form it may be embodied.

In the accompanying one sheet of drawing:

Figure 1 is a side elevation of my mproved spark plug shown in the Wall of an internal combustion engine.

Fig. 2 is vertical section through the plug taken on the line II-II of Fig. 1.

Fig. 3 is a side elevation of the moved from the base shell.

Fig. 4; is an elevation of the insulating element and electrode.

Fig. 5 is a plan view of the bottom of the plug assembled.

In detail the construction illustrated in the drawings includes the outer base shell 1 of the spark plug comprising a cylindrical plug reternally,

shoulder 11.

body of-metal, with a hexagonal portion to provide a grip for a wrench, and having a contracted, externally threaded, tubular stem 2 at one end thereof, adapted to engage the spark plug socket of an internal combustion engine. The shell 1 is threaded inas at 4 at its outer end and has the annular internal flange 5 formed at its mnefi end.

T e retaining shell com rises a hollow c lindrical shell 6 having :in enlarged, he; agonal flange 7 on one end thereof for wrench engagement. Adjacent said flange, the shell 6 s exteriorly threaded at 8 to engage the internally threaded portion 1 of the outer shell 1.

The insulation member 9 consists of a cyllndrical element preferably of porcelain, having a reduced end as at 10, leaving the I The porcelain 9 is secured within the cylindrica shell 6 by interposing the annular flan ed bushin Wall of the shel 6 and t e body of the porcelain 9 both of which it frictionally engages. The annular, internally projecting flange 5 on the bushing engages the shoulder 11. The asbestos or other heat resistin gasket 12, interposed between the flange 5 an the shoulder 11 permits expansion and 12 between the con ucting rod 14 is concentrically located within the porcelain 9 and has the star shaped firing electrode 15 welded or fixedly secured thereon. The opposite end of the rod 14 projects beyond the porcelain and through the conical ca 16 of the refractory material, engaging t e tapered end 17, formed on the porcelain 9. The cap 16 centers the porcelain 9 within the shell 6 by resting in the annular depression 18 turned in the upper face of the flange 7. The- 6 with the internal threads 4 of the outer I shell 1. The reduced end 10 of the porcelain 9, with the star shaped firing points pre'illas vents shocks or strains being transmitted to the (porcelain liable to cause breakage. The

thereon projecting be end the end of the shell 6, extends throng '1 the central opening,

provided in the end of the base 1, and the I shoulder ll thereon engages with the annular internal flan 5, formed in the interior of the said hollow ass 1. The flange is tapered or beveled-internally at 23 surrounding the electrode 15.,

The reduced portion of the porcelain 9 snugly en ages the opening in the shell 6 through w 1ch it passes and the only exposed surface isbetween' the points 23 of the electrode 15 and around the firing point where the flange 5 is chamberedaway at 23'.. The utility of such construction is stronglygine compression and deposits can .collect' with no disrupting action to destroy it. Such'deposits are detrimental to the eflicient operation'of the plug, since carbon deposits are better conductors than the air-gap between the main and ground electrodes.

The flat, star shaped, electrode point is positioned to lie substantially flush with the exposed end of base 1, so that if the plug 1s dropped the exposed parts, upon w ich it would strike, would be of such character as to .be unbreakable. Many standard spark plugs have so much of the porcelain exposed, that the slightest unusual Jar causes a crack which necessitates discarding the porcelain. It is obvious in the improvement I have provided that loss b breakage is negli ible and thus a longer li e of plug is assure messes In the present construction the exposed areaof porcelam s reduced to the minimum conslstent with good 1nsulation;- and is surreducing the tendency to carbon precipitat1ontherein, Multiplication of the discharge points 23, in practice, has proved that the spark travels around from one position another, because of var in electrical conditlons, thus keeping a1 t e points burnedclean, and creating an electrical zone of dlscharge betwen the terminals that has a dlSIllPlilIlg effect upon carbon deposits before their mass can build up to a point of OOIldIlCiJlVlti greaterthan the spark gap.

Hav ng t us described my invention what I claim anddesire to secure by Letters Pat ent is A spark plug such as described comprisin a hollow cylindrical base, externally threa ed, for engagement with the cylinder walls of an lnternal combustion engine; a flange within'said base adjacent one end thereof a hollow shell in threaded engagement with the interior of said cylindrical base on the end opposite said flange; an insulated member frictionally centered within said hollow shell having a shoulder thereon adapted to engage said base flange; a plural pointed flat electrode on said insu ator end flush with the end of said base; a cap housing adapted to center said insulated member withm said hollow shell by engagement with said insulated member and hollow shell and a terminal nut for binding said hollow shell, in-

sulated member and cap housing into an integral unit..

In testimon my hand at 14th day of November, 1919;

RAY L. HULL.

In presence o:E--

ENRY LINCOLN V. J onNsoN.

whereof I have hereunto set an F rancisco, California, this rounded by a zone of electrical disturbance A 

